Sorry, but there is no slider. Also in Ubuntu 11.04 i had the problem, that the brightness slider was not there, when booting up with AC connected. When I booted up on battery the slider was there. I hoped that this was fixed but now i still have a nearly dark screen, when booting up.
–
user31707Nov 1 '11 at 13:29

Anyone coming here with the same problem, check out @dolhow's answer below. That's the one that works.
–
its_meJan 19 '12 at 4:53

11 Answers
11

This is supposed to be configurable in the energy options, set the brightness to the desired level and it will always be used. If you use a laptop you will also need to configure the level for battery mode as well...

I found that Gnome has some issues about lcd panel brightness, e.g. if I run on battery mode and set the brightness manually to a given level and leave the laptop unattended for 10 seconds it will go back to the preset brightness when I take control back. Same goes when on A/C mode except it takes longer so goes unnoticed more easily. I believe all those settings should be saved somewhere and restored - at least for A/C mode.

I was hoping for something that automatically remembers my changes via keyboard shortcuts, but I guess you are right.
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Decio LiraSep 8 '10 at 17:38

5

So the answer is...? Changing it in Screen settings doesn't save it for the next session, and there's nothing in Power options.
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seanmonstarNov 10 '11 at 23:09

As far as I remember, the setting is supposed to be restored/saved between sessions. It has been a while since I last toyed with those settings and I don't have access to a machine running the latest Ubuntu at the moment, maybe this is a new bug?
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levesqueNov 11 '11 at 15:38

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
echo 0 > /sys/class/backlight/acpi_video0/brightness
exit 0

Per @zerdo: In my dell studio 1558 the brightness setting is stored in /sys/class/backlight/intel_backlight/brightness. Just change the path if your computer doesn't use the acpi_video0 folder.

Also, per @Nick :
If this is the only answer you read, note that the 0 in echo 0 is going to be your default brightness setting. I had set this up and it was driving me crazy for a long time : every time I booted up, it would set it to the lowest brightness setting. I prefer mine to start at max brightness, so I used echo 10 instead. Your hardware might vary in brightness scale.

In my dell studio 1558 the brightness setting is stored in /sys/class/backlight/intel_backlight/brightness, just change the path if your computer doesn't use the acpi_video0 folder
–
zurdoFeb 2 '12 at 16:59

If this is the only answer you read, note that the 0 in echo 0 is going to be your default brightness setting. I had set this up and it was driving me crazy for a long time that every time I booted up, it would set it to the lowest brightness setting. I prefer mine to start at max brightness, so I used echo 10 instead. Your hardware might vary in brightness scale.
–
NickFeb 21 '13 at 15:28

and note that you can check /sys/class/backlight/acpi_video0/brightness to see what your current brightness level is. for my ubuntu 14.04, the scale goes from 0-100 and I like to set it at 75.
–
kevinqiJan 6 at 16:09

Command line

If that does not work, you can try to manually set the brightness.

Note: Path may vary with hardware / kernel version, may be /proc/acpi/video0 ..., you may need to browse the /proc/acpi directory to find the brightness setting and adjust the following commands accordingly.

cat /proc/acpi/video/VGA/LCD/brightness

The output of that command varies a bit with hardware, 1 -> 10 , 1 -> 12 , 1 -> 100 ??? Choose a value and set it (choose the value for your hardware).

If you get your setting wrong, most likely you will just loose your display, and have to reboot. As this is a hardware setting, you really need to identify your hardware and research the settings first.

You should never, ever set 'acpi_osi=Linux'. The kernel ACPI code is carefully written to be compatible with Windows, and therefore by default advertises itself at Windows so that the same BIOS functions are used. If you override this, you are doomed to a grab bag of bugs in untested code paths that will never be fixed. Even if you find that acpi_osi=Linux fixes your immediate symptom, you are going to end up with an unsupported mess.
–
slangasekMay 30 '12 at 0:37

Here is a quick workaround for that :-
edit the /etc/rc.local file by typing
sudo gedit /etc/rc.local in terminal
comment out the exit 0 by adding # in the begining such that it looks like this :-

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
#exit 0

this is necessary otherise it wont work !

after this add the following line in the file

echo 0 > /sys/class/backlight/acpi_video0/brightness

such that it looks like this :-

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
#exit 0
echo 0 > /sys/class/backlight/acpi_video0/brightness

replace 0 with the required brightness value ( ranges from 0 to 10 )

save the file and exit.

now try testing the setting by typing this command in terminal

echo 0 > /sys/class/backlight/acpi_video0/brightness

if the brightness changes to minimum , you have got it right !
reboot to see the changes.

Note :- you may have to replace acpi_video0 with your device code if you have a different one ( its mostly acpi_video0 ). Most of u wont need to do so.

Okay, So i attempted to do this and it did not remember it. so after modifying the script I then enter the command "echo 0 > /sys/class/backlight/acpi_video0/brightness" but that does not work, because my/sys/class/backlight directory contains a dell_backlight and a intel_backlight
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philipballewNov 2 '11 at 5:08

I have the same issue, this parameter is not remembered between sessions.
–
levesqueDec 21 '11 at 21:40

The "Screen" option of "System Settings" works OK, and in /sys/class/backlight/acpi_video0/brightness the option also change accordingly, but the problem is that nothing happens with the real brightness.

I found the solution to my problem:

Add the next option under your "Device" section in /etc/X11/xorg.conf and restart:

Option "RegistryDwords" "EnableBrightnessControl=1"

This worked for my NVIDIA card (Ubuntu 11.10 x64 on Toshiba Satellite L745-SP4142CL)

The first thing you need to do is to find out which ACPI interface (acpi_video) controls the brightness. This can be done by looking into your Xorg log file to see which acpi_video was loaded. To do this via command line, simply use the following command: